1. Technical Field
The present invention relates to a flat bottom bag having vertical gussets constructed using a modified vertical form, fill, and seal packaging machine, and the method for making same, that provides for a single piece construction of a stand-up bag suitable for retail snack food distribution. The invention allows for use of existing film converter and packaging technology to produce a stand-up package with minimal increased costs and minimal modifications.
2. Description of Related Art
Vertical form, fill, and seal packaging machines are commonly used in the snack food industry for forming, filling, and sealing bags of chips and other like products. Such packaging machines take a packaging film from a sheet roll and forms the film into a vertical tube around a product delivery cylinder. The vertical tube is vertically sealed along its length to form a back seal. The machine applies a pair of heat-sealing jaws or facings against the tube to form a horizontal transverse seal. This transverse seal acts as the top seal on the bag below and the bottom seal on the package being filled and formed above. The product to be packaged, such as potato chips, is dropped through the product delivery cylinder and formed tube and is held within the tube above the bottom transverse seal. After the package has been filled, the film tube is pushed downward to draw out another package length. A transverse seal is formed above the product, thus sealing it within the film tube and forming a package of product. The package below said transverse seal is separated from the rest of the film tube by cutting horizontally across the sealed area.
The packaging film used in such process is typically a composite polymer material produced by a film converter. For example, one prior art composite film used for packaging potato chips and like products is illustrated in FIG. 1, which is a schematic of a cross-section of the film illustrating each individual substantive layer. FIG. 1 shows an inside, or product side, layer 16 which typically comprises metalized oriented polypropylene (“OPP”) or metalized polyethylene terephtalate (“PET”). This is followed by a laminate layer 14, typically a polyethylene extrusion, and an ink or graphics layer 12. The ink layer 12 is typically used for the presentation of graphics that can be viewed through a transparent outside layer 10, which layer 10 is typically OPP or PET.
The prior art film composition shown in FIG. 1 is ideally suited for use on vertical form and fill machines for the packaging of food products. The metalized inside layer 16, which is usually metalized with a thin layer of aluminum, provides excellent barrier properties. The use of OPP or PET for the outside layer 10 and the inside layer 16 further makes it possible to heat seal any surface of the film to any other surface in forming either the transverse seals or back seal of a package. Alternatively, a material can be used on the outside layer 12 that will not seal on itself, such as a paper layer or a non-sealing polymer layer, so that only the inside layer 16 is used as a sealing surface.
Typical back seals formed using the film composition shown in FIG. 1 are illustrated in FIGS. 2a and 2b. FIG. 2a is a schematic of a “lap seal” embodiment of a back seal being formed on a tube of film, which can be used when the outside and inside layers are sealable together. FIG. 2b illustrates a “fin seal” embodiment of a back seal being formed on a tube of film, which can be used when the outside layer is not suitable as a sealing surface.
With reference to FIG. 2a, a portion of the inside metalized layer 26 is mated with a portion of the outside layer 20 in the area indicated by the arrows to form a lap seal. The seal in this area is accomplished by applying heat and pressure to the film in such area. The lap seal design shown in FIG. 2a insures that the product to be placed inside the formed package will be protected from the ink layer by the metalized inside layer 26.
The fin seal variation shown in FIG. 2b also provides that the product to be placed in the formed package will be protected from the ink layer by the metalized inside layer 26. Again, the outside layer 20 does not contact any product. In the embodiment shown in FIG. 2b, however, the inside layer 26 is folded over and then sealed on itself in the area indicated by the arrows. Again, this seal is accomplished by the application of heat and pressure to the film in the area illustrated.
Regardless of whether a lap seal or fin seal is used for constructing a standard package using a vertical form and fill packaging machine, the end result is a package as shown in FIG. 3a with horizontally oriented top and bottom transverse seals 31, 33. Such package is referred to in the art as a “vertical flex bag” or “pillow pouch,” and is commonly used for packaging snack foods such as potato chips, tortilla chips, and other various sheeted and extruded products. The back seal discussed with reference to FIGS. 2a and 2b runs vertically along the bag and is typically centered on the back of the package shown in FIG. 3a, thus not visible in FIG. 3a. Because of the narrow, single edge base on the package shown in FIG. 3a formed by the bottom transverse seal 33, such prior art packages are not particularly stable when standing on one end. This shortcoming has been addressed in the packaging industry by the development of a horizontal stand-up pouch such as the embodiment illustrated in FIGS. 4a, 4b, and 4c. As can be seen by reference to said figures, such horizontal stand-up pouch has a relatively broad and flat base 47 having two contact edges. This allows for the pouch to rest on this base 47 in a vertical presentation. Manufacture of such horizontal stand-up pouches, however, does not involve the use of standard vertical form, fill, and seal machines but, rather, involves an expensive and relatively slow 3-piece construction using a pouch form, fill, and seal machine.
Referring to FIGS. 4b and 4c, the horizontal stand-up pouch of the prior art is constructed of three separate pieces of film that are mated together, namely, a front sheet 41, a rear sheet 43, and a base sheet 45. The front sheet 41 and rear sheet 43 are sealed against each other around their edges, typically by heat sealing. The base sheet 45 is, however, first secured along its outer edges to the outer edges of the bottom of the front sheet 41 and rear sheet 43, as is best illustrated in FIG. 4c. Likewise, the mating of the base sheet 45 to the front sheet 41 and the rear sheet 43 is also accomplished typically by a heat seal. The requirement that such horizontal stand-up pouch be constructed of three pieces results in a package that is significantly more expensive to construct than a standard form and fill vertical flex bag.
Further disadvantages of using horizontal stand-up pouches include the initial capital expense of the horizontal stand-up pouch machines, the additional gas flush volume required during packaging as compared to a vertical flex bag, increased down time to change the bag size, slower bag forming speed, and a decreased bag size range. For example, a Polaris model vertical form, fill, and seal machine manufactured by Klick Lock Woodman of Georgia, USA, with a volume capacity of 60-100 bags per minute costs in the range of $75,000.00 per machine. A typical horizontal stand-up pouch manufacturing machine manufactured by Roberts Packaging of Battle Creek, Mich., with a bag capacity of 40-60 bags per minute typically costs $500,000.00. The film cost for a standard vertical form, fill, and seal package is approximately $0.04 per bag with a comparable horizontal stand-up pouch costing roughly twice as much. Horizontal stand-up pouches further require more than twice the oxygen or nitrogen gas flush. Changing the bag size on a horizontal stand-up pouch further takes in excess of two hours, typically, while a vertical form and fill machine bag size can be changed in a matter of minutes. Also, the typical bag size range on a horizontal stand-up pouch machine is from 4 oz. to 10 oz., while a vertical form and fill machine can typically make bags in the size range of 1 oz. to 24 oz.
One advantage of a horizontal stand-up pouch machine over a vertical form and fill machine, however, is the relatively simple additional step of adding a zipper seal at the top of the bag for reclosing of the bag. Vertical form and fill machines typically require substantial modification and/or the use of zipper seals premounted on the film oriented horizontally to the seal facings used to seal the horizontal transverse seals.
An alternative approach taken in the prior art to producing a bag with more of a stand-up presentation is the construction of a flat bottom bag such as illustrated in FIG. 3b. Such bag is constructed in a method very similar to that described above with regard to prior art pillow pouches. However, in order to form the vertical gussets 37 on either side of the bag, the vertical form, fill, and seal machine must be substantially modified by the addition of two movable devices on opposite sides of the sealing carriage that moves in and out to make contact with the packaging film tube in order to form the tuck that becomes the gussets 37 shown in FIG. 3b. Specifically, when a tube is pushed down to form the next bag, two triangular shaped devices are moved horizontally towards the packaging film tube until two vertical tucks are formed on the packaging film tube above the transverse seals by virtue of contat with these moving triangular shaped devices. While the two triangular shaped devices are thus in contact with the packaging tube, the bottom transverse seal 33 is formed. The package is constructed with an outer layer 30 that is non-sealable, such as paper. This causes the formation of a V-shaped gusset 37 along each vertical edge of the package when the transverse seals 31, 33 are formed. While the triangular shaped devices are still in contact with the tube of packaging material, the product is dropped through the forming tube into the tube of packaging film that is sealed at one end by virtue of the lower transverse seal 33. The triangular shaped devices are then removed from contact with the tube of packaging film and the film is pushed down for the formation of the next package. The process is repeated such that the lower transverse seal 33 of the package above and upper transverse seal 31 of the package below are then formed. This transverse seal is then cut, thereby releasing a formed and filled package from the machine having the distinctive vertical gussets 37 shown in FIG. 3b. 
The prior art method described above forms a package with a relatively broad base due to the V-shaped vertical gussets 37. Consequently, it is commonly referred to in the art as a flat bottom bag. Such flat bottom bag is advantageous over the previously described horizontal stand-up pouch in that it is formed on a vertical form, fill, and seal machine, albeit with major modifications. However, the prior art method of making a flat bottom bag has a number of significant drawbacks. For example, the capital expense for modifying the vertical form, fill, and seal machine to include the moving triangular-shaped devices is approximately $30,000.00 per machine. The changeover time to convert a vertical form, fill, and seal machine from a standard pillow pouch configuration to a stand-up bag configuration can be substantial, and generally in the neighborhood of one-quarter man hours. The addition of all of the moving parts required for the triangular-shaped device to move in and out of position during each package formation cycle also adds complexity to the vertical form, fill, and seal machine, inevitably resulting in maintenance issues. Importantly, the vertical form, fill, and seal machine modified to include the moving triangular-shaped devices is significantly slower than a vertical form, fill, and seal machine without such devices because of these moving components that form the vertical gussets. For example, in the formation of a six inch by nine inch bag, the maximum run speed for a modified vertical form, fill, and seal machine using the triangular-shaped moving devices is in the range of 15 to 20 bags per minute. A standard vertical form, fill, and seal machine without such modification can construct a similarly sized pillow pouch at the rate of approximately 40 bags per minute.
Consequently, a need exists for a method to form a stand-up pouch, similar in appearance and functionality to the prior art horizontal stand-up pouches or prior art flat bottom bags, using vertical form, fill, and seal machine technology and a single sheet of packaging film. This method should allow for reduced film cost per bag as compared to horizontal stand-up pouches, ease in size change, and little capital outlay, all while maintaining bag forming speeds typical of vertical form, fill, and seal machine pillow pouch production. Such method should ideally produce a flat bottom bag constructed of material commonly used to form standard vertical flex bags without adding complexity or moving parts to a standard vertical form, fill, and seal machine.